An electron field emitter is a key component in phosphor display technology. Current phosphorous field emission displays require the electron field emitter to be enclosed in a high vacuum and ultra-clean environment. Such an environment is necessary to avoid the rapid deterioration of the types of cathodes currently being used in phosphor displays. Typically these cathodes have a pointed or conical shaped tip.
When a potential is applied between the anode and cathode, cathodes having a pointed or conical tip advantageously concentrate the electrical field strength around the tip. Consequently, relatively small potentials (e.g., less than about 10 Volts) between the cathode and anode of the display are needed to cause the emission of electrons. The ability to use such low potentials has an important benefit because conventional CMOS devices can operate at these low potentials, and therefore can be used to control the emission of electrons.
The use of pointed or conically shaped cathode tips has a major drawback however. The performance of the cathode deteriorates as material deposits on the tip and thereby changes the shape of the tip. Material from the anode can deposit on the cathode tip due to sputtering caused by electrons emitted from the cathode and hitting the anode. Additionally, contaminants remaining or leaking inside the chamber that encloses the cathode can deposit on the cathode tip.
A change in the shape of the cathode tip can change the density of the field around the tip, thereby changing the location from which electrons are emitted. This, in turn, defocuses the phosphor display. Eventually the performance of the cathode deteriorates to the point where the phosphorous display no longer operates within acceptable limits. Decreasing the rate of deterioration by enclosing the electron field emitter in an even cleaner environment or higher vacuum is a major cost in the fabrication of phosphorous displays, and it is becoming prohibitively expensive to improve upon existing vacuum technologies to improve cathode lifetime.
Accordingly, what is needed in the art is an electron field emitter device that can operate in environments that are easy to achieve and has a long lifetime, while not experiencing the above-mentioned problems.